Polymers, such as polyurethanes, are well known in the art, as are various methods of making such polymers. In particular, it is known to modify polymers through use of additives to produce a desired property in the polymer for use in varying applications. Some examples of these polymers are as follows.
U.S. Pat. No. 5,512,655 discloses a process for the production of polyurethanes from dihydroxyfatty acids and/or dihydroxypolyfatty acids by reacting an isocyanate, a polyol, and a dihydroxyfatty acid formed by ring opening an epoxidized fatty acid, as well as a polyurethane product usable in thixotropic pastes.
U.S. Pat. No. 5,476,343 discloses an improved, thermally insulated, impact and abrasion resistant pipeline and low conductivity, flexible cementitious material using a polymeric modifier. The pipeline includes 25 to 40 percent fly ash cenospheres, glass microspheres or a combination of the two. The reference further discloses conventional pipelines having flexible coatings of solid, elastomers or elastomers filled and extended with other low density materials, such as polyurethane elastomers filled with glass micro-spheres.
U.S. Pat. No. 5,473,043 discloses moisture-curable urethane resins having urethane prepolymers, a blocked amine compound, and an inorganic filler treated with an organic compound, such as a variety of calcium carbonates treated with a fatty acid, a fatty acid ester, a titanium compound, a silane, and a surface active agent. The urethane resin may contain a variety of additives, one of which is a thixotropic agent at least. The filler is at least 5 parts by weight, and preferably at least 10 parts by weight, to avoid having the filler settle during storage and forming a hard cake at the bottom of the storage container. The reference also notes that anti-settling agents may be used to prevent the filler from settling, but that this often results in retarding curing or affecting storage stability.
U.S. Pat. No. 5,433,872 discloses a grease composition having 75 to 95 parts by weight of a base component of a liquid or semi-solid polyol based polyurethane having about 1 to 15 parts by weight of a thickening agent such as colloidal silica particles, and an antioxidant.
U.S. Pat. No. 5,344,673 discloses spherical resin particles and methods of making same, by preparing a micro-dispersion of a condensation polymer and permitting the micro-dispersed particles to coalesce by maintaining ions on the surface of the particles, where urethane resins are the preferred particle material.
U.S. Pat. No. 5,071,683 discloses a method and device for forming a gellified polyurethane layer on a surface by spraying a mixture of polyol and isocyanates having a viscosity between 20 and 2,000 centipoise, thereby avoiding the micro air-bubbles that form using a conventional technique.
U.S. Pat. No. 4,592,961 discloses a liquid coating formulation having a homogeneous solution of solvent, an aromatic polyester resin and vinylidene chloride copolymer, and a quantity of particles having an average diameter of less than about 15 microns. Sufficient homogeneity is desired, and this feature is best tested by avoiding formation of micro-bubbles.
U.S. Pat. No. 4,927,861 discloses a rigid polyurethane foam having a low density ranging from 0.20 to 1.30 g/cm.sup.3, which is prepared by reacting at least one polyether polyol and at least one polyester polyol, a hydroxyl, and an aromatic polyisocyanate, such as diphenylmethane diisocyanate (MDI), and the combinations that can be injection molded to form various parts of conventional articles.
U.S. Pat. No. 4,525,386 discloses a technique for enhancing open-celled polyurethane foam by impregnating the foam with filler particles having the desired properties, wherein the filler particles may be micron sized microspheres of glass, metal powders, or other additives, depending on the property to be enhanced.
U.S. Pat. No. 4,252,658 discloses a solid lubricant having carbon micro-spheres of 0.1 to 1,000.mu. and a specific gravity of 0.2 to 2.0, and wherein the carbonizable material may be a thermosetting resin, a crosslinkable high molecular weight compound, or an organic high molecular weight compound, such as a polyurethane like polyethylene methylenebis(4-phenyl) carbamate.
U.S. Pat. No. 4,157,907 discloses a method of forming a moldable material in the form of coated glass particles by producing the glass in a kiln, crystallizing and grinding the glass to a smaller size, and adding a thermosetting organic resin binder, which may be a thermosetting binder or a curable plastic such as polyurethane resins. This produces molding compositions having a high content of crystallizable glass particles without impairing their moldable properties and mechanical characteristics.
It is desired, however, to make and use low density polymers, in particular low density polyurethanes, by including a filler in the polymer composition. It would also be desirable to produce a low density polymer that is stable over long time periods.